Leshem Guy, Richman Michal, Lisniansky Elvira, Antman-Passig Merav, Habashi Maram, Gräslund Astrid, Wärmländer Sebastian K T S, Rahimipour Shai
Department of Chemistry , Bar-Ilan University , Ramat-Gan 5290002 , Israel . Email:
Department of Biochemistry and Biophysics , Arrhenius Laboratories , Stockholm University , S-106 91 Stockholm , Sweden . Email:
Chem Sci. 2018 Oct 3;10(1):208-217. doi: 10.1039/c8sc01992d. eCollection 2019 Jan 7.
The self-assembly of Aβ to β-sheet-rich neurotoxic oligomers is a main pathological event leading to Alzheimer's disease (AD). Selective targeting of Aβ oligomers without affecting other functional proteins is therefore an attractive approach to prevent the disease and its progression. In this study, we report that photodynamic treatment of Aβ in the presence of catalytic amounts of chlorin e6 can selectively damage Aβ and inhibit its aggregation and toxicity. Chlorin e6 also reversed the amyloid aggregation process in the dark by binding its soluble and low molecular weight oligomers, as shown by thioflavin T (ThT) fluorescence and photoinduced cross-linking of unmodified protein (PICUP) methods. Using HSQC NMR spectroscopy, ThT assays, amino acid analysis, SDS/PAGE, and EPR spectroscopy, we show that catalytic amounts of photoexcited chlorin e6 selectively damage the Aβ histidine residues H6, H13, and H14, and induce Aβ cross-linking by generating singlet oxygen. In contrast, photoexcited chlorin e6 was unable to cross-link ubiquitin and α-synuclein, demonstrating its high selectivity for Aβ. By binding to the Aβ histidine residues, catalytic amounts of chlorin e6 can also inhibit the Cu-induced aggregation and toxicity in darkness, while at stoichiometric amounts it acts as a chelator to reduce the amount of free Cu. This study demonstrates the great potential of chlorin e6 as a multifunctional agent for treatment of AD, and shows that the three N-terminal Aβ histidine residues are a suitable target for Aβ-specific drugs.
淀粉样蛋白β（Aβ）自组装成富含β-折叠的神经毒性寡聚体是导致阿尔茨海默病（AD）的主要病理事件。因此，选择性靶向Aβ寡聚体而不影响其他功能蛋白是预防该疾病及其进展的一种有吸引力的方法。在本研究中，我们报告在催化量的二氢卟吩e6存在下对Aβ进行光动力处理可选择性地损伤Aβ并抑制其聚集和毒性。如硫黄素T（ThT）荧光和未修饰蛋白质的光诱导交联（PICUP）方法所示，二氢卟吩e6在黑暗中也通过结合其可溶性和低分子量寡聚体来逆转淀粉样聚集过程。使用HSQC核磁共振光谱、ThT测定、氨基酸分析、SDS/PAGE和电子顺磁共振光谱，我们表明催化量的光激发二氢卟吩e6选择性地损伤Aβ组氨酸残基H6、H13和H14，并通过产生单线态氧诱导Aβ交联。相比之下，光激发的二氢卟吩e6无法使泛素和α-突触核蛋白交联，证明了其对Aβ的高选择性。通过与Aβ组氨酸残基结合，催化量的二氢卟吩e6还可以在黑暗中抑制铜诱导的聚集和毒性，而化学计量的二氢卟吩e6则作为螯合剂来减少游离铜的量。本研究证明了二氢卟吩e6作为治疗AD的多功能药物的巨大潜力，并表明三个N端Aβ组氨酸残基是Aβ特异性药物的合适靶点。
